Carrageenan-containing product and a method of producing same

ABSTRACT

A method of producing a carrageenan-containing product comprising reacting a carrageenan-containing seaweed starting material in a substantially homogenous mixture of a solvent in which carrageenan is substantially insoluble, and an alkaline aqueous phase, ans subjecting the reacted and washed seaweed to shear stress, and a carrageenan-containing product obtainable by the method.

FIELD OF THE INVENTION

The present invention relates to a method for the production of acarrageenan-containing product derived from seaweed and to acarrageenan-containing seaweed product prepared by the method.

BACKGROUND OF THE INVENTION

Carrageenan is a complex mixture of sulphated polysaccharides comprisinglinear polymers of 1,3 bound β-D-galactose units and 1,4 boundα-D-galactose units with the following generalised structure:

    →3α)A(1→4β)B(1→3α)A(1→4β)B (1→3α)A(1→4β)B(1→3α)A(1→4.beta.)B(1→

in which A and B represent galactose derivatives from two differentgroups. The molecular weight of useful commercial carrageenan isgenerally from about 500,000 to about 1,000,000. Polymers with amolecular weight below about 100,000 are not generally classified ascarrageenan. Carrageenan is used extensively in the food industry as anemulsifier, a gelling agent and as a thickening agent.

Carrageenan is normally soluble in warm water, in which it forms highviscosity solutions, and insoluble in most organic solvents. All typesof carrageenans form complexes with proteins.

Portions of the polymer chains in some types of carrageenan (kappa/iota)can form double helix structures and thus a 3-dimensional network whichresults in gel formation. Carrageenan gels are thermoreversible. Thetemperature at which the transition from gel to sol occurs (the gel'smelting point) is between 40° C. and 70° C., depending upon theconcentration and presence of cations.

Different types of carrageenan known as kappa, iota, lambda, ny and mycarrageenan are known. The different types are differentiated accordingto the nature of their repeating galactose units. The most importantcarrageenan types for commercial purposes are kappa, iota and lambdacarrageenan (Kirk-Othmer (ed): Encyclopedia of Chemical Technology, 3rdedition, 1980, p. 53).

In aqueous solution the various types of carrageenan react differentlytowards different cations as follows:

    ______________________________________                                        kappa carrageenan:                                                                           precipitates (gels) with K.sup.+, Ca.sup.++,                                  Mg.sup.++, Ba.sup.++, Sr.sup.++  and NH.sub.4.sup.+ and is                    in-                                                                           soluble in solutions containing these                                         ions. The strongest gelation is                                               achieved with K.sup.+. No gelation occurs                                     with Na.sup.+, and Na salts are soluble.                       lambda carrageenan:                                                                          does not precipitate (gel) with the                                           cations listed above. All salts are                                           soluble.                                                       iota carrageenan:                                                                            essentially like kappa carrageenan,                                           but, the strongest gelation is                                                achieved with Ca.sup.++.                                       ______________________________________                                    

These properties can be employed for selective extraction of kappa/iotaand lambda carrageenan (see e.g. Smith et al., Can. J. Chem. 33, 1352(1955)).

Carrageenan containing galactose units which are sulfated in the6-position can form 3,6-anhydro units (elimination of sulphate by ringformation) by treatment with a base. It is possible employing such amodifying alkaline treatment to provide a carrageenan material withimproved gel properties, assuming the carrageenan contains 6-sulphatedgalactose units.

The polymer chains in carrageenan can be broken by treatment with anacid (hydrolytic depolymerization) or by treatment with hydrogenperoxide (oxidative depolymerization). By use of a modifying alkalinetreatment as well as a hydrolytic or oxidative depolymerizationcarrageenan products having optimum gelation properties and viscosityfor specific purposes may be obtained.

Carrageenan is found in seaweed of the class Rhodophyceae (red algae)from which it can be isolated. Carrageenan does not exist as a freepolymer in the red algae, but comprises a part of the "skeleton" of thealgae.

The occurrence and distribution of the various carrageenan types inRhodophyceae is dependent on, among other things, the species, locationand life cycle of the seaweed. Carrageenan is found in species belongingto the families Gigartinaceae and Solieriaceae and particularly in thespecies belonging to the genera Gigartina, Chondrus, Eucheuma andIridaea.

Red algae of the family Gigartinaceae, e.g. Chondrus crispus andGigartina stellata, synthesize kappa and lambda carrageenan in differentgrowth stages: kappa carrageenan in the male and female stage and lambdacarrageenan in the asexual growth stage. The lambda/kappa ratio inisolated carrageenan from a species of algae is thus effected by therelative dominance of one or the other growth stage at the time thealgae is "harvested" as well as by the location at which the algaegrows. By use of vegetative propagation of algae from a given growthstage it is possible to obtain an algal material which is consistentwith regard to content and distribution of carrageenan. Algae isolatedfrom a given growth stage can be propagated vegetatively, thusmaintaining this stage, thereby making it possible to obtain an algalmaterial with a desired content of a given carrageenan type.

Red algae from the family Solieriaceae, e.g. Eucheuma cottonii andEucheuma spinosum, synthesize essentially kappa and iota carrageenan,respectively.

The taxonomy of the seaweed genera and species, especially the generaGigartina and Iridaea, is a matter of discussion. The Gigartina radulaspecies are often identified as one or more Iridaea species.Furthermore, commercial designations differing from the supposedbotanical names are often used causing identification problems. In thepresent context the supposed botanical names are used.

The traditional process for the production of commercial carrageenanproducts comprises extraction of carrageenan from fresh or dried seaweedin hot water at a basic pH. The aqueous extract, which contains about 1%carrageenan, is filtered to remove insoluble material (cellulose,hemicellulose, etc.). The filtered extract, which optionally can beconcentrated to about 4% and subjected to various purificationtreatments such as filtering with activated carbon, bleaching, etc., isthen treated with an alcohol or with a salt to precipitate thecarrageenan. Carrageenan prepared in this manner is generally referredto as "purified carrageenan" (PC).

The production of PC requires high energy consumptions and may involvesubstantial environmental pollution and therefore, several attempts havebeen made to provide less costly carrageenan-containing products. Suchproducts, which are generally referred to as "semi-refined carrageenan"(SRC) are commercially available. Specific types of SRC are also knownas "KOH-treated seaweed", "alkali-treated carrageenan", "PhilippineNatural Grade" (PNG) , and "Processed Eucheuma Seaweed" (PES). SRC isprepared by heat-treating whole seaweed in aqueous alkaline solutionsunder conditions which modify the carrageenan by at least partiallyremoving sulphate groups.

Examples of such SRC products are disclosed in JP 57.19942 describing amethod in which algae are heat treated in an aqueous solution ofpotassium carbonate and sodium hydroxide, following which the algalmaterial is washed several times with water and potassium dihydrogenphosphate solution and finally dried and crushed to give the productwhich may e.g. be applied in jams and pet food; U.S. Pat. No. 4,443,486which discloses a carrageenan-containing stabilizing agent for use inmilk-based products, prepared by alkali treatment of seaweed of thespecies Eucheuma cottonii, and in JP 53.107990 disclosing a method inwhich an algal material is treated with an aqueous potassium hydroxidesolution at 70°-95° C., after which the treated material is washed withwater and comminuted. The product may be used as a silkworm feed.

U.S. Pat. No. 3,849,395 discloses a process which comprises heating ahydrocolloid in an aqueous alkaline medium followed by hydrolyzing in anacidic medium.

However the known processes or the production of SRC products involvesat least the following disadvantages:

(i) the treatment in the heated alkaline solution may result in acertain disintegration of the seaweed structure which inevitably leadsto release of carrageenan whereby the solution becomes highly viscousand the yield of carrageenan the final products is reduced,

(ii) they are not generally suitable, especially not when seaweedspecies having a high content of lambda carrageenan is used as thestarting material, since this species of carrageenan will be eluted inthe alkaline solution and the use of pure sodium-containing alkalinesubstances will lead to loss of dissolved carrageenan,

(iii) the resulting SRC products have a limited range of applicationsprimarily due to their high content of cellulose structures and otherinsoluble seaweed substances giving an undesired "cloudiness" in theproducts in which they are used.

The present invention provides solutions to the above problems. Inparticular, there is provided a method for the production of acarrageenan-containing seaweed product, comprising treating the seaweedstarting material in a substantially homogeneous alkaline mixturecontaining a solvent in which carrageenan is substantially insoluble,and subjecting the treated seaweed material to shear stress in a heatedstate.

The method according to the invention results in a higher yield ofcarrageenan in the resulting products relative to the known processesfor preparing SRC, since substantially no loss of carrageenan occurs,irrespective of the species of carrageenan contained in the seaweedstarting material. Furthermore, the shear stress treatment results incarrageenan-containing products which are substantially withoutoff-taste and which are less coloured than known commercially availablesemirefined carrageenan products and, additionally, having improvedswelling and hydration properties, thereby providing an "instantizing"carrageenan product. It is a further advantage that products accordingto the invention may be used for the preparation of water gels withimproved appearances.

BRIEF DISCLOSURE OF THE INVENTION

Accordingly, the present invention relates in one aspect to a a methodof producing a carrageenan-containing product comprising the steps of

(1) reacting a seaweed starting material containing carrageenan, in asubstantially homogeneous alkaline mixture of a solvent in whichcarrageenan is substantially insoluble, and an aqueous phase comprisingan alkaline substance, to obtain at least partial formation in thecarrageenan of 3,6-anhydro units,

(2) separating the seaweed material from the reaction mixture of step(1) and subjecting it to at least one washing step with a solvent/watermixture, and

(3) subjecting the seaweed material resulting from step (2) to shearstress.

In another aspect the invention provides a carrageenan-containingproduct obtainable by a method as defined herein which, (i) whenmeasuring a 2-3 wt % suspension of the product having a dry mattercontent of at least 90 wt % and an average particle size of less than0.18 mm, in a 0.7 wt % aqueous solution of KCl by means of a BranderViscograph operated at 60 rpm and at a heating rate of 1.5° C./min froman initial temperature of 35° C., shows a maximum swelling at atemperature which is at the most 65° C., preferably at the most 62° C.,more preferably at the most 58° C., most preferably at the most 54° C.and in particular at the most 50° C. and which, (ii) when measured inthe form of a water gel containing 0.126% dry matter of the product bymeans of a spectrophotometer at a wavelength of 420 nm in a cuvette witha light path of 1 cm exhibits a light transmission of at least 5%,preferably at least 7% and more preferably at least 10%.

DETAILED DISCLOSURE OF THE INVENTION

As mentioned above, the method of the invention involves reacting acarrageenan-containing seaweed starting material in a substantiallyhomogeneous alkaline mixture as defined herein. In the present context,the term "substantially homogeneous" refers to the fact that the mixtureof solvent and aqueous alkaline phase exists as a single liquid phase ona macroscopic level, containing both the water and the solvent. In otherwords, separation of the mixture into a macroscopic aqueous phase and amacroscopic solvent phase must not take place while the seaweed materialis being reacted in the mixture. This is a prerequisite for the properfunctioning of the method, since phase separation on a macroscopic levelresults in a situation where the seaweed material is found primarily inthe aqueous phase, leading to water absorption and ultimately todissolution of the seaweed structure and a loss of carrageenan. Themixture is preferably a solution, the preferred mixtures thus beingsystems in which the water, the solvent, the alkaline substance and anysalt present are mutually soluble at the temperature and pressure inquestion. This is discussed in greater detail below. However, it is alsocontemplated that macroscopically homogeneous mixtures which are notsolutions, but which are homogeneous suspensions or emulsions, can beused. Furthermore, while the alkaline mixture should for the purposes ofthe present invention be substantially homogeneous, a certain minorphase separation can generally be accepted as long as the polarity ofthe reaction medium lies sufficiently below the limit at which theseaweed material swells excessively and disintegrates.

As will be further explained below, the preferred homogeneous solutionis obtained by carefully controlling the relationship between the waterconcentration, the solvent concentration, the alkaline substanceconcentration and the salt concentration.

The solvent used in the alkaline mixture and/or in any washingtreatments subsequent to the reaction with the alkaline mixture may beany solvent which fulfills the following conditions:

Carrageenan must be substantially insoluble or at the most only slightlysoluble in the solvent, since the method is based upon an alkalinemodification of the carrageenan as defined above taking place at itsnatural location in the seaweed, i.e. in situ. Any carrageenan that isdissolved by the solvent will tend to be lost to the reaction mixture,thereby decreasing the yield of carrageenan in the final product. Afurther disadvantage resulting from dissolved carrageenan is anincreased viscosity of the reaction mixture which makes separation ofthe treated seaweed material difficult.

The solvent should preferably be water-miscible, so as to enable ahomogeneous mixture to be prepared and maintained without the use ofe.g. an emulsifier or excessive agitation.

The solvent must allow the seaweed to be maintained in a structurallyessentially intact condition. This is due to the fact that the alkalinemodification of the carrageenan is dependent upon the seaweed beingswollen and permeable, so as to allow passage of reagents (the alkalinesubstance) into the seaweed as well as passage of dissolved matter (i.e.dissolved cellulose, coloring matter, protein, starch, etc.) out of theseaweed. However, since the carrageenan matrix functions as a"container" in which the modification reaction takes place, thestructure of this matrix must remain intact and must not disintegrate,as disintegration results in the formation of a paste which is difficultto handle.

The conditions which should be fulfilled by solvents used in the methodof the invention are described in detail below together with a testwhich may be used to determine whether a given solvent is suitable in agiven system.

The same solvent may be used in the above homogeneous alkaline mixtureand for any subsequent washing treatments, or one solvent may be usedfor the heat treatment and another solvent, or optionally more than onesolvent, may be used for the washing treatments.

The solvent may be a monohydric alcohol including methanol, ethanol,isopropanol, tert-butanol, sec-butanol, n-butanol, tert-amyl alcohol,neopentyl alcohol, sec-amyl alcohol or diethyl carbinol; a dihydricalcohol, such as ethylene glycol, propylene glycol or tetramethyleneglycol; a trihydric alcohol including glycerol; a ketone, for exampleacetone, methyl ethyl ketone, methyl iso-butyl ketone or methyltert-butyl ketone; or a glycol ether such as diethylene glycolmonomethylether, ethylene glycol monoethylether, diethylene glycolmono-methylether or triethylene glycol dimethylether. Mixtures of two ormore of the above solvents may also be employed in the alkaline mixtureor in any solvent/water mixture.

The base used for in the above step of alkaline modification of theseaweed starting material may suitably be a hydroxide or carbonate of analkali metal, an alkaline earth metal or ammonium, for example sodiumhydroxide, potassium hydroxide, barium hydroxide, calcium hydroxide,magnesium hydroxide, sodium carbonate, potassium carbonate, bariumcarbonate, calcium carbonate, magnesium carbonate, ammonium hydroxide orammonium carbonate; an alkali metal alcoholate, for example sodiummethoxide, sodium ethoxide or sodium isopropoxide; a basic inorganicphosphate, for example calcium phosphate, magnesium phosphate, trisodiumphosphate or tripotassium phosphate; or a quaternary ammonium hydroxide,for example tetramethyl ammonium hydroxide, trimethylethyl ammoniumhydroxide, tetrabutyl ammonium hydroxide or tetraethyl ammoniumhydroxide. A combination of more than one of the above bases may also beused.

When "water" is referred to herein in connection with the amounts ofwater, seaweed, solvent and base in the reaction mixture of the seaweedstarting material and the substantially homogeneous mixture, the amountof water is the sum of added water and water present in the seaweedstarting material. Thus, when dried seaweed is treated, it may benecessary to add water either directly or by first soaking the driedseaweed in a saline solution (e.g. a sodium or potassium chloridesolution). On the other hand, when fresh seaweed is used, the amount ofwater to be added will be determined taking into consideration the watercontent of the seaweed. In certain cases the method may be performedwithout added water, in which case the only water present in thesubstantially homogeneous alkaline mixture is that which is contained inthe fresh seaweed or in dried seaweed which has been soaked in a salinesolution.

As mentioned above, one of the advantages of the method of the inventionis that an increased yield of carrageenan is obtained compared to knownmethods for producing semirefined and purified carrageenan products.This is partially due to the fact that the method of the invention istypically carried out on a relatively large amount of dry matter, basedon the weight of reaction mixture, i.e. the starting material and thesubstantially homogeneous solvent/aqueous alkaline phase mixture.Typically, the content of seaweed dry matter in the reaction mixture isin the range of 5 to 20 wt % and preferably in the range of 10 to 15 wt%. In contrast, the prior art methods for the production of purifiedcarrageenan are generally only able to work with dry matter contents ofabout 1-4%.

In order to improve the stabilization capacity and gel strength of thecarrageenan polymer, which is in a highly concentrated suspension in aswollen condition but in an insoluble form (gel), it is necessary tocarefully control the coherence of the seaweed material during thereaction in the above step (1). The tendency of the various seaweedtypes to swell up is dependent upon the temperature, the polarity of theliquid phase and the cation concentration.

In the following, a relatively simple test is described which may beused to determine a solvent's suitability for maintaining asolvent/water mixture's polarity within a range in which the seaweedmaterial swells and absorbs the reaction mixture (the base), while atthe same time preventing disintegration of the seaweed at thetemperature in question and allowing a sufficient amount of the base tobe dissolved so as to provide an acceptable reaction time:

a mixture of the solvent and water (135 g, containing the type andamount of solvent to be tested) is mixed in a 150 ml 3-necked flask andheated while stirring to the temperature at which base modification isto take place (a salt such as sodium chloride may be added to themixture, depending on whether such a salt is to be present during thebase modification). A conductivity electrode is placed at the surface ofthe mixture and the base to be used is added gradually while stirringslowly. When the conductivity changes abruptly, the point has beenreached at which the reaction medium begins to separate into two phases,an aqueous bottom phase with a high base content and a top phasecontaining the majority of the solvent and having a low baseconcentration. The concentration of the solvent, water and the base isplotted in a phase diagram for the chosen salt content. If a given baseconcentration (enabling a single liquid phase to be maintained) issufficient for the desired reaction, 15 g of chopped seaweed material isadded while stirring slowly.

a color change from red to green for seaweed material of the familyGigartinaceae indicates that the base has penetrated into the seaweedmaterial, and the amount of liquid that can be drained from the seaweedafter heat treatment for a few minutes corresponds to the amount ofliquid which has been absorbed. To check for possible incompleteswelling, samples can be taken and investigated under a microscope forred areas into which the base has not penetrated. To check for possibledissolution of the seaweed material, the drained off liquid phase isrefrigerated; if carrageenan has been lost to the liquid due todissolution of the seaweed, this will be shown by gelation in the cooledliquid.

For seaweed of the family Solieriaceae (Eucheuma spp.), in which thealgal pigment does not have such characteristic indicator properties,thin slices of the material are prepared using a razor blade after a fewminutes of heat treatment, a universal indicator (dissolved in ethanol)which is effective in the pH range of 4-11, is added and the slices areobserved under a microscope. Possible dissolution of the seaweedmaterial may be determined as explained above, i.e. by observation forgelation in the cooled liquid.

The above-described test procedure, i.e. the color test fordetermination of the amount of base absorbed, the tendency of the cooledliquid to gel, and the base concentration which can be achieved in thereaction medium, gives a qualitative indication of a solvent'ssuitability for use in the method of the invention and allows thedetermination of acceptable base, solvent and salt concentrations forthe solvent in question.

In certain preferred embodiments, the weight ratio between solvent andwater in the reaction mixture is from 5:95 to 50:50, such as from 10:90to 40:60, e.g. from 12:88 to 30:70 and including from 15:85 to 25:75.

The concentration of the alkaline substance in the reaction mixture ofstep (1) as defined above is typically between 0.25M/kg liquid phase to3.0M/kg liquid phase, preferably between 0.7M/kg liquid phase to 1.5M/kgliquid phase.

In addition, the reaction mixture may, if desired, contain furthersubstances such as anti-foaming agents, as well as neutral salts, e.g.selected from the group consisting of neutral salts of K, Na, Ca, Mg andBa.

The reaction of the seaweed starting material may advantageously becarried out at a temperature in the range of 50°-150° C. such as in therange of 80°-100° C. and at a pressure of from about atmosphericpressure to about 3 atm for a period of about 15 min to 30 h, typicallyfrom about 1 h to about 6 h.

After reacting the seaweed starting material as defined above, thereacted seaweed is separated from the reaction mixture, e.g. by drainingor filtering, after which the reacted seaweed is washed in a firstsolvent/water mixture, e.g. at a temperature in the range of 20°-100°C., preferably in the range of 50°-80° C., so as to remove the alkalinereagents as well as dissolved impurities. The solvent/water mixture mayalso be used to enable an ion exchange of the product to take place byadding soluble salts to the wash. Both PC and SRC produced by the priorart methods will have a certain predetermined cation composition. By useof the method of the invention, however, it is possible to control thecation content of the final product, which is clearly advantageous sinceit allows the product to be designed according to the intended use.Thus, the first solvent/water mixture and any additional solvent/watermixture may, if desired, contain added neutral salts, e.g. selected fromthe group consisting of neutral salts of K, Na, Ca, Mg and Ba.

The first solvent/water mixture will typically, although notnecessarily, contain the same solvent as the substantially homogeneousalkaline mixture, and the concentration of the solvent in the firstsolvent/water mixture will typically be as high as or higher than theconcentration of the solvent concentration in the substantiallyhomogeneous alkaline mixture. The weight ratio between solvent and waterin the first solvent/water mixture is typically from 15:85 to 60:40,more typically from 20:80 to 50:50, more typically from 25:75 to 40:60.The first wash as well as any subsequent washes will typically takeplace at atmospheric pressure, although a pressure of more than 1 atmmay be used, and for a period of at least about 5 minutes for each wash,more typically at least about 10 minutes for each wash.

After washing in the first solvent/water mixture, the treated seaweed isseparated from the mixture and is preferably subjected to at least oneadditional wash in an additional solvent/water mixture, in order toremove as much of the alkaline reagents and dissolved impurities aspossible. Typically, the treated seaweed is subjected to two additionalwashes (i.e. a total of three washes), but further washes may of coursebe used. It has been found using the method of the invention that afterthree washes, the reacted seaweed is generally essentially free of thealkaline reagent used for modification of the carrageenan. The weightratio between solvent and water in any additional solvent/water mixtureis typically from 25:75 to 99:1.

The additional washes are carried out in essentially the same manner asthe first wash. However, the concentration of the solvent in a second orfurther wash will typically be as high as or higher than theconcentration used in the preceding wash.

The reacted and washed seaweed material may subsequently be subjected toa drying step such as vacuum evaporation, fluid bed drying using air ata temperature of e.g. about 90° C. for e.g. about 20 min, or byconventional air drying at e.g. 40°-60° C. The material may be dried toa dry matter content of at least 25 wt %, preferably at least 30 wt %and more preferably at least 40 wt %.

The reacted and washed seaweed material may be ground to a suitableparticle size, e.g. using known procedures for grinding.

The separated reacted seaweed material resulting from the above step (2)is subjected to a shear stress at a temperature typically in the rangeof 20° to 200° C., preferably in the range of 40° to 175° C., morepreferably in the range of 75° to 150° C. and most preferably in therange of 85° to 125° C. The separated treated seaweed material issubjected to shear stress for a period of time being in the range of 10to 200 seconds, preferably in the range of 10 to 100 seconds and morepreferably in the range of 20 to 40 seconds. The shear stress can beprovided by means of an extruder or a shear mixer.

When the seaweed material is subjected to shear stress at least onefurther added substance may be added. The further substance may beselected from inorganic acids, bases and salts and emulsifiers such asmono- and diglycerides, sorbitan esters, polysorbates, sucrose esters,citric acids of mono- and diglycerides, polyglycerol esters of fattyacids, propylene glycol monostearate, lactic acid esters, and lecithins,non-carrageenan hydrocolloids such as pectin, agar, alginate, locustbean gum, guar gum, gum arabic, and gelatine and anti-microbial agentssuch as benzoic acid, parabens, sorbic acid, propionic acid, sulphurdioxide, acetic acid and formaldehyde, flavouring agents, and colouringaaents.

When the carrageenan-containing product is obtained by means of anextruder the carrageenan-containing product may be provided as anextruded string having a diameter of 2 mm, preferably 4 mm, morepreferably 6 mm and most preferably 8 mm; as extruded particles having aspherical form and a diameter of at least 2 mm, preferably 4 mm, morepreferably 6 mm and most preferably 8 mm; and as extruded particleshaving random forms and sizes.

The seaweed material resulting from the above-mentioned process may besubjected to a further process step selected from comminution, e.g.grinding, mincing, cutting and further conventional methods and dryingas described above to a dry matter content of at least 80 wt %,preferably at least 85 wt %. such as at least 90 wt %, including atleast 95 wt %.

The carrageenan-containing seaweed product prepared by the above methodcontains relatively few impurities e.g. starch as solid particles,cellulose and substances which might confer undesired coloring effectsand undesired flavouring, the product may comply with current standardsfor use in food products. The carrageenan-containing seaweed productproduced by the method of the invention is therefore fully suitable,without further purification, for use in the majority of products inwhich carrageenan is employed. However, if desired it may also readilybe subjected to further purification to produce a further purifiedcarrageenan.

It is contemplated that further purification of the presentcarrageenan-containing product may be performed by dissolving either thecarrageenan-containing seaweed material which is obtained after thewashing steps or the carrageenan-containing seaweed product which isobtained after being subjected to shear stress, in water, heating thesolution at a temperature in the range of 70°-100° C., filtering thesolution, concentrating the filtered solution, mixing the concentratedsolution with a solvent to precipitate the purified carrageenan, e.g.using a solvent:solution ratio of from 1:1 to 1:3, separating thepurified carrageenan from the solution, and drying the purifiedcarrageenan.

Purification may also e.g. be performed using potassium chlorideprecipitation. This typically involves spraying the carrageenan extractinto a continuously flowing stream of a potassium chloride solution witha concentration of about 3.5-7%. The precipitated gel is then pressed,optionally frozen and thawed, dried and finally ground.

As mentioned above, the present invention also relates to a shearstress-treated carrageenan-containing seaweed product obtainable by theabove-described method. As it has been defined, such a product maybecome more readily hydrated and solubilized in water relative to thereacted and washed seaweed material prior to being subjected to shearstress. When expressed in terms of the temperature at which maximumswelling occurs with the above-defined method of measuring, thetemperature at which this occurs with the shear stress- treated productis at least 4° C. lower, preferably at least 6° C. lower, morepreferably at least 8° C. lower, most preferably at least 10° C. lowerand in particular at least 12° C. lower. In a preferred embodiment thistemperature is at least 14° C., more preferably at least 16° C. lowerand most preferably at least 18° C. lower, such as 20° C. lower.

The product according to the present invention contains substantiallyless non-carrageenan substances (impurities) than prior art semi-refinedcarrageenan products and it is essentially free of off-flavor. When theproduct is provided in powdery form it is cream-colored.

In preferred embodiments, the present carrageenan-containing seaweedproduct when produced from a seaweed species of the family Gigartinaceaewill typically have a content of acid insoluble matter (AIM) of at themost 2% by weight. The content of acid insoluble matter is preferably atthe most 1.5% by weight, preferably at the most 1.2% by weight, morepreferably at the most 1.0% by weight. Furthermore, these products havea low protein content, the nitrogen content typically being at the most0.25% by weight, preferably at the most 0.20% by weight, and morepreferably at the most 0.15% by weight; a low cellulose content, i.e.typically at the most 2.0% by weight, preferably at the most 1.5% byweight, more preferably at the most 1.0% by weight; and a low starchcontent, i.e. typically at the most 10% by weight.

The carrageenan-containing seaweed product produced from a seaweedspecies of the family Solieriaceae has a nitrogen content typicallybeing at the most 0.25% by weight, preferably at the most 0.20% byweight, more preferably at the most 0.15% by weight; a content ofcellulose of at the most 9.0% by weight, preferably at the most 7.0% byweight, more preferably at the most 6.0% by weight, most preferably atthe most 5.0% by weight; a starch content of at the most 4.5% by weight,preferably at the most 2.5% by weight, more preferably at the most 1.5%by weight; and an acid insoluble matter content of at the most 13.0% byweight, preferably at the most 10% by weight and more preferably 8% byweight;

The present invention is further illustrated by the following examplesand Figures in which

FIG. 1 shows a microscopic presentation of a typical non-extrudedproduct at a magnification of 250x,

FIG. 2 shows a microscopic presentation of a typical extruded product amagnification of 250x,

FIG. 3 shows a microscopic presentation of a typical non-extrudedproduct at a magnification of 1000x, and

FIG. 4 shows a microscopic presentation of a typical extruded product ata magnification of 1000x.

MATERIALS AND METHODS

Determination of nitrogen content

The values given in the examples for nitrogen content were determinedusing the Kjeldahl method.

Determination of sodium, potassium and calcium content

A sample of the product is ashed by weighing the sample into a porcelaincrucible which is placed in a furnace preheated to 600° C. and left toash overnight. The crucible is then transferred to a desiccator, cooledand weighed. The ashed material is dissolved in HNO₃ and is diluted toan appropriate concentration. The concentration of sodium, potassium andcalcium, respectively, is determined using Flame Atomic AbsorptionSpectroscopy by means of Varian SpectrAA 400.

Determination of cellulose content

The cellulose content is determined as the difference between theglucose content after hydrolysis in 12M H₂ SO₄ and the glucose contentafter hydrolysis in 2M H₂ SO₄ (Englyst procedure)

2×100.0 mg of the sample is weighed in a test tube with a screw top. 5ml of 12M H₂ SO₄ is added to one of the test tubes, which is placed in awater bath at 35° C. for one hour and shaken every 10 minutes. 25 ml ofwater is then added and the test tube is placed in a water bath at 100°C. with agitation for 1 hour. 30 ml of 2M H₂ SO₄ is added to the othertest tube, which is then placed in a water bath at 100° C. for one hour.Both test tubes are then allowed to cool and the contents are diluted atleast 5 times for enzymatic determination of the glucose content.

Determination of the glucose content is performed by adding 5 ml of anenzyme solution (glucose oxidase) to 250 ml of a sample to be tested ora standard. After 60 minutes, the absorbency is measured at 334 nm. Theglucose concentration of the samples is determined using a standardcurve.

The cellulose content (%) is calculated according to the followingequation: ##EQU1## in which D₁ and D₂ are dilution factors, and G₁ andG₂ are the weight in grams of the samples.

Determination of starch content

An appropriate sample of the carrageenan- and starch-containing productis treated with amyloglucosidase (supplied by Boehringer) in a solutionof water and dimethyl sulfoxide at pH 5-6 whereby the starch content istransformed into glucose.

The glucose content is determined as described above (cf. determinationof cellulose).

Determination of acid insoluble matter (AIM)

The method used for the determination of acid insoluble matter isdescribed in Food Chemical Codex (FCC), 1st Edition, p. 393.

1.5000 g of the sample to be tested is weighed in a 250 ml beaker, towhich 135 ml distilled water and 15 ml 10% H₂ SO₄ is added. The beakeris covered with a watch glass and the solution is boiled using a sandbath or a water bath for 6 hours, the sides of the beaker being scrapedat regular intervals with a spatula with a piece of rubber tubingattached. Distilled water corresponding to the amount of water which hasevaporated is added, and at the end of the 6 hours 0.5000 g of filterearth is added. The solution is filtered through a dried and weighedBuchner filter with a filter plate at the bottom, and the residue iswashed several times with warm distilled water. The glass filter is thendried for 3 hours at 105° C., cooled in a desiccator and weighed after 3hours. The content of acid insoluble matter is calculated on the basisof the weight of the sample before and after boiling in the sulphuricacid solution.

Determination of viscosity

Aqueous solutions containing 1.5% by weight of the carrageenan productand 0.193% by weight of CaCl₂.2H₂ O (corresponding to 3.5% Ca calculatedon the carrageenan product) were prepared at a temperature of 75° C. Bymeans of a Brookfield LVT viscometer, using an appropriate spindle, theviscosity of the solution was measured at a temperature of 75° C. and 60rpm. Spindle no. 1 was used when the readings were less than 100 cP, andspindle no. 2 was used when the readings were higher than 100 cP.

Determination of gel strength

Aqueous solutions containing 1.26% dry matter of the carrageenan productby weight of the carrageenan product (dry matter content 90%), 0.162% byweight of CaCl₂.2H₂ O (corresponding to 3.5% Ca calculated on thecarrageenan product) and 0.667% by weight of KCl were prepared at atemperature of 90° C. and filled into two cylindrical (diameter 8 cm,height 4.5 cm) glass dishes. The surface of the solution was coveredwith thin circular sheet of plastic foil to prevent evaporation andformation of air bubbles. After cooling at ambient temperature untilnext day a gel was formed. After having removed the plastic foil the gelstrength (expressed in g) was measured in the centre of each gel bymeans of a Stevens Texture Analyzer using the following analyticalparameters:

    ______________________________________                                        Plunger:           12 mm diameter                                             Distance:          6 mm                                                       Speed:             0.5 mm/sec                                                 ______________________________________                                    

Determination of turbidity of water gels

The water-gels are prepared in the same way as the water-gels fordetermination of gel strength (as disclosed above), the only differencebeing that no CaCl₂.2H₂ O is added and the cooling is provided in acuvette having the dimensions of 1*1 cm. When cooled to room temperaturethe transmission of light is measured by means of a spectrophotometer(Spectronic 2000) at a wave length of 420 nm. The transmission of lightis measured in two directions being at right angles to each other.

    ______________________________________                                        Non-extruded carrageenan-containing seaweed products:                                                     % T < 5                                           Extruded carrageenan-containing seaweed products:                                                         % T > 5                                           ______________________________________                                    

EXAMPLES Example 1

Dried seaweed material of the species Iridaea ciliata, Iridaealaminarioides, collection 1, Iridaea laminarioides, collection 2 andGigartina skottsbergii, having dry matter contents of 80.5% to 94.8% byweight was broken into pieces of 2 to 5 cm. Using a 20 l closedstainless steel reactor with heating mantel and stirrer the seaweedmaterial of either species was treated under stirring with a mixturecomprising potassium hydroxide, isopropanol and water at a temperatureof 82° C.

The composition of the reaction mixture is shown in Table 1.

During the reaction, samples of the seaweed material were withdrawn fromthe reaction mixture after 1, 3, 5, 7, and 9 hours. The samples werewashed three times using 30%, 40%, and 50% by weight, respectively, ofisopropanol/water mixtures under stirring at a temperature of 75° C. Thesamples were dried at 40° C. to a dry matter content of 88% to 90% byweight followed by grinding to a particle size of less than 0.18 mm.

The gelling and thickening properties of the carrageenan products weretested in demineralized water (cf. Table 2 and 3).

                  TABLE 1                                                         ______________________________________                                        The composition of the reaction mixture                                                        I. lamina-  I. lamina-                                                        rioides     rioides                                                                              G. skotts-                                         I. ciliata                                                                            coll. 1     coll. 2                                                                              bergii                                    ______________________________________                                        Seaweed dry                                                                            2710    2710        2673   2765                                      matter, g                                                                     wt %     13.6    15.1        13.4   13.8                                      Anhydrous                                                                              1119    986         1114   1119                                      KOH, g                                                                        wt %     5.6     5.5         5.6    5.6                                       Isopro-  4042    3560        4053   4029                                      panol, g                                                                      wt %     20.2    19.8        20.3   20.1                                      Water g  12128   10679       12160  12087                                     wt %     60.6    59.5        60.8   60.4                                      ______________________________________                                    

                  TABLE 2                                                         ______________________________________                                        Viscosity (expressed in cP) of the carrageenan                                products obtained in Example 1 measured in demineralized                      water at 75° C. and 60 rpm                                                     Reaction time                                                         Species   1 hrs    3 hrs  5 hrs   7 hrs                                                                              9 hrs                                  ______________________________________                                        I. ciliata                                                                              172.0    106.0  60.3    34.9 28.2                                   I. laminari-                                                                            49.8     37.7   31.1    24.0 20.4                                   oides, coll. 1                                                                I. laminari-                                                                            21.4     16.7   13.7    11.0 --                                     oides, coll. 2                                                                G. skotts-                                                                              329.0    174.0  85.3    54.1 41.9                                   bergii                                                                        ______________________________________                                    

                  TABLE 3                                                         ______________________________________                                        Gel strength (expressed in g) of the carrageenan                              products obtained in Example 1 measured in demineralized                      water                                                                                 Reaction time                                                         Species   1 hrs    3 hrs  5 hrs   7 hrs                                                                              9 hrs                                  ______________________________________                                        I. ciliata                                                                              365      440    360     295  275                                    I. laminari                                                                             330      340    315     270  255                                    oides. coll. 1                                                                I. laminari                                                                             200      225    200     160  --                                     oides. coll. 2                                                                G. skotts 190      195    190     170  155                                    bergii                                                                        ______________________________________                                    

Example 2

Dried seaweed materials of the species Iridaea ciliata and Gigartinaskottsbergii with dry matter contents of about 83% by weight were brokeninto pieces of 2 to 5 cm. Using the reactor from Example 1 the seaweedmaterial was treated under stirring with potassium hydroxide inisopropanol and water, at a temperature of 82° C.

The composition of the reaction mixture is shown in Table 4.

After the reaction the solvent mixture was drained off through thebottom valve of the reactor and the treated seaweed material was washedunder stirring with isopropanol/water mixtures, with and withoutpotassium chloride added, at a temperature of 75° C. according to thescheme shown in Table 5.

The washed seaweed material was finally dried at a temperature of 40° C.to a dry matter content of 88-90% by weight followed by grinding to aparticle size of less than 0.18 mm.

Yields and the analytical characteristics of the products are shown inTable 6.

                  TABLE 4                                                         ______________________________________                                        The composition of the reaction mixture                                                Gigartina skotts-                                                    Reaction   bergii             Iridaea ciliata                                 time       7 hrs   7 hrs      5 hrs 5 hrs                                     ______________________________________                                        Seaweed dry                                                                              1844    1844       2723  1806                                      matter, g                                                                     wt %       9.5     9.5        13.6  9.0                                       Anhydrous  1114    1114       1114  1114                                      KOH, g                                                                        wt %       5.7     5.7        5.6   5.6                                       Isopro-    4000    4000       4110  4270                                      panol, g                                                                      wt %       20.5    20.5       20.6  21.4                                      Water, g   12542   12542      12048 12810                                     wt %       64.3    64.3       60.3  64.1                                      ______________________________________                                    

                  TABLE 5                                                         ______________________________________                                        Washing Procedures                                                                        Gigartina skotts-                                                             bergii         Iridaea ciliata                                    Reaction time 7 hrs  7 hrs     5 hrs                                                                              5 hrs                                     ______________________________________                                        30 wt % aqueous                                                                             1X     1X                                                       isopropanol                                                                   35 wt % aqueous                                                                             1X     1X                                                       isopropanol                                                                   40 wt % aqueous                                                                             1X     1X        2X   2X                                        isopropanol                                                                   50 wt % aqueous                1X   1X                                        isopropanol                                                                   30 wt % aqueous      1X             1X                                        isopropanol +                                                                 5 wt % KCl                                                                    ______________________________________                                    

                  TABLE 6                                                         ______________________________________                                        Yields and characteristics of the carrageenan pro-                            ducts obtained in Example 2                                                              Gigartina skotts-                                                             bergii          Iridaea ciliata                                    Reaction time                                                                              7 hrs   7 hrs     5 hrs                                                                              5 hrs                                     ______________________________________                                        Yield, g     1351    1410      950  1004                                      Cellulose, wt %                                                                            <1.0    --        1.0  --                                        Acid Insoluble                                                                             --      <0.5      --   --                                        Matter (AIM),                                                                 wt %                                                                          Calcium, wt %                                                                              0.44    0.36      0.60 0.50                                      Sodium, wt % 0.90    0.24      1.22 0.26                                      Potassium, wt %                                                                            8.69    13.75     8.92 14.10                                     ______________________________________                                    

Example 3

Dried seaweed of the species Gigartina skottsbergii having a dry mattercontent of 77.1% by weight was cut into pieces of 5 to 10 mm. 441.8 g ofa 27% (w/w) mixture of methanol in water was transferred to a 2 l3-necked reaction flask equipped with a mechanical stirrer, a refluxcondenser and a heating mantle and 35.5 g of potassium hydroxide (85%)was added slowly while stirring gently. When the base was dissolved, 60g of the dried seaweed was added to the solution and the temperature wasincreased to the reflux temperature of 83.2° C. The mixture was refluxedfor 3 hours while stirring slowly.

The liquid phase was drained off through a fine sieve (1 mm) and theseaweed material was returned to the flask and covered with 300 g of a30% (w/w) isopropanol/water mixture. While stirring slowly the mixturewas kept at a temperature of 75° C. for 30 minutes. The mixture wasagain drained through the same sieve and the washing procedure wasrepeated twice with a 35% and 40% (w/w) isopropanol/water mixture,respectively.

The obtained carrageenan product was dried at 40° C. to a dry mattercontent of about 90% and ground to a particle size of less than 0.18 mm.

The characteristics of the product are shown in Table 7.

Example 4

A carrageenan product was prepared essentially as described in Example3, the only difference being that the dried seaweed material (60 g) wastreated with an aqueous alkaline organic solvent mixture (441.8 g) inwhich methanol was replaced by acetone. The mixture was refluxed for 6hours at a reflux temperature of 63.5° C.

The characteristics of the product are shown in Table 7.

Example 5

A carrageenan product was prepared essentially as described in Example3, the only difference being, that the dried seaweed material (60 g) wastreated with an aqueous alkaline organic solvent mixture (441.8 g) inwhich methanol was replaced by ethanol. The mixture was refluxed for 3hours at the reflux temperature of 84.8° C.

The characteristics of the product are shown in Table 7.

                  TABLE 7                                                         ______________________________________                                        Characteristics of the carrageenan products obtained                          in Examples 3, 4, and 5                                                                  Exam. 3   Exam. 4 Exam. 5                                          ______________________________________                                        Dry matter, wt %                                                                           89.9        90.8    90.7                                         Acid Insoluble                                                                             1.0         2.0     0.5                                          Matter (AIM) wt %                                                             Nitrogen, wt %                                                                             0.11        0.13    0.07                                         Starch, wt % 4.6         4.5     4.5                                          Viscosity, cP                                                                              75.0        131.0   73.6                                         Gel strength, g                                                                            270.0       260.0   255.0                                        ______________________________________                                    

Example 6

A carrageenan product was prepared essentially as described in Example3, the only differences being that the dried seaweed material (60 g) wastreated with an aqueous alkaline organic solvent mixture (441.8 g) inwhich methanol was replaced by isopropanol and the potassium hydroxidewas replaced by 48.5 g potassium phosphate (K₃ PO₄.3H₂ O). The mixturewas refluxed for 19 hours at the reflux temperature of 82° C.

The product was dried at 40° C. to a dry matter content of 91.4% andground to a particle size of less than 0.18 mm.

The characteristics of the product were:

    ______________________________________                                        Acid Insoluble Matter (AIM), wt %                                                                  1.0                                                      Nitrogen, wt %       0.21                                                     Starch, wt %         3.4                                                      Viscosity, cP        25.0                                                     Gel strength, g      330.0                                                    ______________________________________                                    

Example 7

One part of dried seaweed of the species G. skottsbergii and I.laminarioides, collection 1, respectively, was pretreated by washingwith 10-12 parts of an aqueous solution containing 10 wt % potassiumchloride at ambient temperature.

The wet pre-washed seaweed was cut into pieces of 5-10 cm and 45 kg ofthis seaweed, comprising 35 wt % dry matter was transferred to a closedreactor equipped with a stirring equipment and a heating mantle. Amixture comprising 20.0 kg 80 wt % isopropanol, 9.5 kg 46 wt % potassiumhydroxide and 5.5 kg water was added to the seaweed under stirring andheating conditions. The solution was drained off and the seaweedmaterial was washed with a solution of aqueous isopropanol (30 wt %)followed by two washing steps, each washing step with a solution of 30wt % isopropanol and 70% of a 3.5 wt % solution of sodium chlorideexcept that sodium chloride was replaced by 3.5 wt % potassium chloridein the second washing step of the seaweed material of Gigartinaskottsbergii. When drained off the seaweed was dried to a dry mattercontent of about 87-90% by weight.

Table 8 shows the reaction conditions for these experiments and Table 9shows the characteristics of the products.

                  TABLE 8                                                         ______________________________________                                        Dry matter content of the seaweed in the reaction                             mixture, reaction temperature and time and                                    yield of Experiment 7                                                                                 reaction                                                          seaweed     temperature                                                       dry matter  (°C.)/                                                                           yield                                       Species     wt %        time (hrs)                                                                              wt %                                        ______________________________________                                        G. skottsbergii                                                                           18.3        90/3      67.8                                        I. laminarioides                                                                          19.0        82/1.5    69.2                                        ______________________________________                                    

                  TABLE 9                                                         ______________________________________                                        Characteristics of the carrageenan products produced                          according to conditions defined in Table 8                                                   G. skotts-                                                                           I. lamina                                                              bergii rioides                                                 ______________________________________                                        Viscosity, cP    50.8     51.8                                                Nitrogen, wt %   0.05     0.15                                                Cellulose, wt %  1.0      1.1                                                 Acid Insoluble   0.8      2.0                                                 Matter (AIM), wt %                                                            Sodium wt %      2.04     5.7                                                 Potassium wt %   7.2      3.9                                                 Calcium wt %     0.35     0.47                                                ______________________________________                                    

Seaweed of the species EUCHEUMA COTTONII

Partly dried seaweed of the species Eucheuma cottonii having a drymatter content of 60 wt % to 75 wt % was washed in a 3.5 wt % sodiumchloride solution to remove sand and other impurities adhering to theseaweed and then chopped into pieces of about 2 cm. The washed seaweedmaterial was dried to a dry matter content of 92.7 wt %. By analysis thedried seaweed material was found to contain 5.5 wt % sodium (Na), 2.2 wt% potassium (K), 0.25 wt % calcium (Ca), 4.6 wt % chloride (Cl⁻), 0.4 wt% nitrogen (N), 2.0 wt % starch, 8.0 wt % cellulose and 8.65 wt % acidinsoluble matter (AIM).

This seaweed material was used as starting material in the followingexamples 8-12.

Example 8

Dried seaweed (55 g) of the species Eucheuma cottonii was added to a 1litre 3-necked reaction flask equipped with a mechanical stirrer,vertical condenser and heating mantle. The seaweed was stirred at atemperature of 82° C. for 3 hours with a homogeneous alkaline mixturecomprising water (302.0 g), isopropanol (100.7 g) and potassiumhydroxide (32.3 g, 85 wt %, 0.489M).

Table 10 shows the composition of the reaction mixture during the heattreatment.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture and twice with 40 wt % isopropanol/water mixture. The washingswere carried out at a temperature of 60° C. for 15 minutes while gentlystirring the mixture. After each washing procedure the solvent mixturewas drained off.

Finally, the washed seaweed material was dried at a temperature of 40°C. giving 41.2 g product which was ground to a particle size of lessthan 0.075 mm.

The characteristics of the product are shown in table 11.

Example 9

Dried seaweed (55 g) of the type Eucheuma cottonii was added to a 1litre 3-necked reaction flask as used in Example 8 and was treated at atemperature of 82° C. with a homogeneous alkaline mixture comprisingwater (280 g), isopropanol (120 g), sodium hydroxide (12.68 g, 0.317M)and potassium hydroxide (11.24 g, 85 wt %, 0.170M).

After 50 minutes of heat treatment the reaction mixture was a sticky andlumpy mass of a nearly disintegrated seaweed material and dissolvedcarrageenan.

The reaction mixture was not worked up.

Table 10 shows the composition of the mixture during the heat treatment.

This experiment was carried out using a reaction mixture in which thealkaline mixture did not fulfill the requirements for homogeneity in thereaction mixture and, therefore, a phase separation of the reactionmixture was obtained.

Example 10

Dried seaweed (55 g) of the type Eucheuma cottonii was added to a 1litre 3-necked reaction flask of same type as in Example 8 and wastreated for a period of one hour and 45 minutes at a temperature of 82°C. with a homogeneous alkaline mixture comprising water (300 g),isopropanol (100 g), sodium hydroxide (12.68 g, 0.317M) and potassiumhydroxide (11.24 g, 85 wt %, 0.170M).

Table 10 shows the composition of the mixture during the heat treatment.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture and twice with 35 wt % isopropanol/water mixture. The washingswere carried out at 60° C. for 15 minutes following the same proceduresas in Example 8.

Finally, the washed seaweed material was dried at a temperature of 40°C. and ground to a particle size of less than 0.075 mm.

The characteristics of the product are shown in table 11.

This Experiment was carried out during almost the same conditions as inExample 2 but with the obvious difference that the alkaline reactionmixture was homogeneous.

Example 11

Dried seaweed (55 g) of the species Eucheuma cottonii was treatedessentially as described in example 10, the only difference being thatthe homogeneous alkaline mixture comprised water (300 g), isopropanol(100 g), sodium hydroxide (11.70 g, 0.293M) and potassium hydroxide(12.85 g, 85 wt %, 0.195M).

During the heat treatment the seaweed was strongly swelled but showed notendency to disintegrate.

Table 10 shows the composition of the mixture during the heat treatmentand the characteristics of the product are shown in table 11.

Example 12

A semirefined carrageenan product was prepared essentially as describedin Example 11, the only difference being that the heat treatment timewas 3 hours and 15 minutes.

During the heat treatment the seaweed was strongly swelled but showed notendency to disintegrate into a sticky and lumpy mass.

Table 1 shows the composition of the mixture during the heat treatmentand the characteristics of the product obtained are shown in table 11.

                  TABLE 10                                                        ______________________________________                                        THE COMPOSITION OF THE REACTION MIXTURE                                       Examples                                                                              8        9       10      11    12                                     ______________________________________                                        Seaweed,                                                                              50.98    50.98   50.98   50.98 50.98                                  dry matter,                                                                   (g)                                                                           Water (g)                                                                             310.86   285.71  305.71  305.95                                                                              305.95                                 Isopro- 100.70   120.00  100.00  100.00                                                                              100.00                                 panol (g)                                                                     Hydroxide                                                                             0.489    0.487   0.487   0.488 0.488                                  (OH.sup.-), M                                                                 Sodium  0.132    0.449   0.449   0.425 0.425                                  (Na.sup.+), M                                                                 Potassium                                                                             0.520    0.201   0.201   0.226 0.226                                  (K.sup.+), M                                                                  Molar ratio                                                                           0.25     2.23    2.23    1.88  1.88                                   Na:K                                                                          ______________________________________                                    

                  TABLE 11                                                        ______________________________________                                        CHARACTERISTICS OF THE PRODUCTS OBTAINED IN                                   EXAMPLES 8 AND 10-12                                                          Examples       8      10        11   12                                       ______________________________________                                        Dry matter, wt %                                                                             89.8   89.6      90.1 90.4                                     Starch, wt %   1.5    2.3       1.6  2.5                                      Cellulose, wt %                                                                              8.4    8.2       8.6  8.6                                      Acid insoluble 12.8   x         x    x                                        matter (AIM), wt %                                                            Nitrogen, wt % 0.10   0.13      0.10 0.10                                     Sodium, wt %   0.58   2.7       2.3  2.2                                      Potassium, wt %                                                                              6.3    3.3       3.6  3.6                                      Calcium, wt %  0.11   0.12      0.13 0.12                                     Chloride, wt % <0.05  <0.05     <0.05                                                                              <0.05                                    Molar ratio    0.16   1.39      1.09 10.4                                     Na:K                                                                          ______________________________________                                    

SEAWEED OF THE SPECIES EUCHEUMA SPINOSUM

Partly dried seaweed of the species Eucheuma spinosum having a drymatter content of 60 wt % to 75 wt % was washed in a 3.5 wt % sodiumchloride solution to remove sand and other impurities adhering to theseaweed and then chopped into pieces of about 2 cm. The seaweed materialwas dried to a dry matter content of 94.2 wt %. By analysis the driedseaweed material was found to contain 4.1 wt % sodium (Na), 6.5 wt %potassium (K), 0.55 wt % calcium (Ca), 4.8 wt % chloride (Cl⁻), 0.64 wt% nitrogen (N), 2.0 wt % starch, 4.7 wt % cellulose and 6.4 wt % acidinsoluble matter (AIM).

This seaweed material was used as starting material in the followingexamples 13-17.

Example 13

Dried seaweed (50 g) of the species Eucheuma spinosum was added to a 1litre 3-necked reaction flask equipped with a mechanical stirrer, refluxcondenser and heating mantle. The seaweed was stirred at a temperatureof 82° C. for 3 hours with a homogeneous alkaline mixture comprisingwater (312.8 g) isopropanol (104.3 g) and potassium hydroxide (32.9 g,85 wt %, 0.498M).

Table 12 shows the composition of the reaction mixture during the heattreatment.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture and twice with 40 wt % isopropanol/water mixture. The washingswere carried out at a temperature of 60° C. for 15 minutes while gentlystirring the mixture. After each washing procedure the solvent mixturewas drained off.

Finally, the washed seaweed material was dried at a temperature of 40°C. giving 31.4 g product which was ground to a particle size of lessthan 0.075 mm.

The characteristics of the product are shown in table 13.

Example 14

Dried seaweed (100 g) of the type Eucheuma spinosum was added to a 1litre 3-necked reaction flask as used in Example 8 and was treated for aperiod of two hours and 15 minutes at a temperature of 82° C. with ahomogeneous alkaline mixture comprising water (635.3 g), isopropanol(211.8 g), sodium hydroxide (20.0 g, 0.5M) and potassium hydroxide (32.9g, 85 wt %, 0.498M).

Table 12 shows the composition of the mixture during the heat treatment.During the heat treatment the seaweed was strongly swelled but showed notendency to disintegrate.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture at a temperature of 60° C. for 15 minutes, once with 40 wt %isopropanol/water mixture at a temperature of 65° C. for 15 minutes andonce with 40 wt % isopropanol/water mixture at a temperature of 40° C.for 15 minutes.

Finally, the washed seaweed material was dried at a temperature of 40°C. and ground to a particle size of less than 0.075 mm.

The characteristics of the product are shown in table 13.

Example 15

Dried seaweed (50 g) of the type Eucheuma spinosum was added to a 1litre 3-necked reaction flask as used in Example 8 and was treated for aperiod of three hours at a temperature of 82° C. with a homogeneousalkaline mixture comprising water (318.6 g), isopropanol (106.2 g),sodium hydroxide (12.0 g, 0.3M) and potassium hydroxide (13.2 g, 85 wt%, 0.200M).

Table 12 shows the composition of the mixture during the heat treatment.During the heat treatment the seaweed was strongly swelled but showed notendency to disintegrate.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture at a temperature of 60° C. for 15 minutes, and twice with 40 wt% isopropanol/water mixture at a temperature of 60° C. for 15 minutes.

Finally, the washed seaweed material was dried at a temperature of 40°C. and ground to a particle size of less than 0.075 mm.

The characteristics of the product are shown in table 13.

Example 16

Dried seaweed (50 g) of the type Eucheuma spinosum was treatedessentially as described in Example 15, the only difference being thatthe homogeneous alkaline mixture comprised water (319.6 g), isopropanol(106.5 g), sodium hydroxide (14.0 g, 0.35M) and potassium hydroxide(9.88 g, 85 wt %, 0.15M).

Table 12 shows the composition of the mixture during the heat treatment.During the heat treatment the seaweed was strongly swelled but nodisintegration could be observed.

After completion of the reaction the solvent mixture was drained off andthe treated seaweed was washed twice with 30 wt % isopropanol/watermixture at a temperature of 60° C. for 15 minutes, once with 40 wt %isopropanol/water mixture at a temperature of 65° C. for 15 minutes andonce with 40 wt % isopropanol/water mixture at a temperature of 60° C.for 15 minutes.

Finally, the washed seaweed material was dried at a temperature of 40°C. and ground to a particle size of less than 0.075 mm.

The characteristics of the product are shown in table 13.

Example 17

Heat treatments as described in the previous Examples 13-16 of the driedseaweed (50 g) of the species Eucheuma spinosum with homogeneousalkaline mixtures using a molar ratio of sodium hydroxide:potassiumhydroxide equal to or greater than about 4 resulted in excessivedisintegration of the seaweed giving a sticky and lumpy reaction mixture

                  TABLE 12                                                        ______________________________________                                        THE COMPOSITION OF THE REACTION MIXTURE                                       Examples     13      14        15    16                                       ______________________________________                                        Seaweed, dry 47.1    94.2      47.1  47.1                                     matter, (g)                                                                   Water, (g)   320.6   646.0     323.5 323.9                                    Isopropanol, (g)                                                                           104.3   211.8     106.2 106.5                                    Hydroxide, M 0.499   0.998     0.500 0.500                                    Sodium, M    0.089   0.678     0.389 0.439                                    Potassium, M 0.582   0.664     0.283 0.233                                    Molar ratio, Na:K                                                                          0.15    1.02      1.37  1.88                                     ______________________________________                                    

                  TABLE 13                                                        ______________________________________                                        CHARACTERISTICS OF THE PRODUCTS OBTAINED IN                                   EXAMPLES 13-16                                                                Examples       13     14        15   16                                       ______________________________________                                        Dry matter, wt %                                                                             90.8   90.0      89.9 90.4                                     Starch, wt %   4.3    3.5       3.3  2.6                                      Cellulose, wt %                                                                              5.6    4.8       4.9  4.7                                      Acid insoluble 7.6    x         x    x                                        matter (AIM), wt %                                                            Nitrogen, wt % 0.10   0.09      0.11 0.10                                     Sodium, wt %   0.54   2.4       2.9  3.4                                      Potassium, wt %                                                                              9.2    6.1       5.3  4.5                                      Calcium, wt %  0.38   0.51      0.42 0.32                                     Chloride, wt % <0.05  <0.05     <0.05                                                                              <0.05                                    Molar ratio, Na:K                                                                            0.10   0.67      0.93 1.28                                     ______________________________________                                    

Example 18

One part by weight of dried seaweed of the species Gigartinaskottsbergii having a dry matter content of about 80% by weight waspre-treated at ambient temperature by washing with 10-12 parts by weightof an aqueous solution containing 10 wt % potassium chloride.

The wet pre-washed seaweed was cut into pieces of 1-5 cm, and 35 kg ofthis seaweed comprising about 30 wt % dry matter was transferred to aclosed reactor equipped with a stirrer and a heating mantle. A mixturecomprising 12.0 kg of isopropanol, 7.8 kg of 46 wt % potassium hydroxideand 26.0 kg of water was added to the seaweed. The mixture was heatedunder stirring. After stirring for 2 hours at 95° C. the mixture wascooled to about 80° C., and the solution was drained off.

Table 14 shows the composition of the reaction mixture during the heattreatment.

The treated seaweed material was then washed three times with an aqueoussolution of isopropanol (30 wt %) under stirring at a temperature of 82°C. for 30 minutes. After each washing step the solution was drained off.Finally, the seaweed material was washed once with an aqueous solutionof isopropanol (10 wt %) containing potassium chloride (5 wt %) understirring at ambient temperature for 30 minutes.

The washing solution was drained off and the majority of the product waspartly dried at a temperature of 50° C. for 1 hour at a slightly reducedpressure to remove the organic solvent giving a product with a drymatter content of 37.5 wt %. For purposes of comparison a smaller partof the washed seaweed was dried at a temperature of 40° C. for about 24hours to a dry matter content of 92.3 wt % and ground to a particle sizeof less than 0.180 mm.

The semi-dried product was subjected to shear stress in a heated statebefore extrusion by means of an experimental extruder (BrabenderEXTRUDIOGRAPH 19/25, where 19 is the diameter in mm of the screw, and 25is the ratio between the length and the diameter of the screw; screw:4:1 DZ mixer; die-type: round die, diameter 4 mm).

The semi-dried product was fed to the extruder at a flow rate of 15-30g/min and processed under the following conditions:

    ______________________________________                                        Temperature of extruder:                                                      ______________________________________                                        Near the feed inlet:     77-78° C.                                     Central zone:            123-124° C.                                   Near the discharge end:  128-129° C.                                   Internal pressure near the discharge end:                                                              10-11 bar                                            Number of revolutions:   39 rpm                                               Torque:                  4-5 Nm                                               Back force:              0.3-0.4 kN                                           ______________________________________                                    

The product was discharged as a gel string which after cooling andhardening was cut into pieces and dried at a temperature of 40° C. to adry matter content of 93.6 wt % followed by grinding to a particle sizeof less than 0.18 mm.

The viscosity of the product was measured and the result is shown intable 15 together with the viscosity of the non-extruded product.

Example 19

Dried seaweed of the species Gigartina skottsbergii was treatedessentially as described in example 18, the only difference being thatthe reaction mixture was supplemented with 1.0 kg of sodium hydroxide(50 wt %).

Table 14 shows the composition of the reaction mixture during the heattreatment.

A semi-dried product with a dry matter content of 41.4 wt % wasobtained. For purposes of comparison a smaller part of this product wasdried to a dry matter content of 93.3 wt % and ground to a particle sizeof less than 0.180 mm.

The semi-dried product was fed to the same extruder as used in example18 and processed under the following conditions:

    ______________________________________                                        Temperature of extruder:                                                      ______________________________________                                        Near the feed inlet:     74-75° C.                                     Central zone:            117-118° C.                                   Near the discharge end:  130-131° C.                                   Internal pressure near the discharge end:                                                              15-16 bar                                            Number of revolutions:   39 rpm                                               Torque:                  6-7 Nm                                               Back force:              0.4-0.5 kN                                           ______________________________________                                    

After drying the extruded product followed by grinding to a particlesize less than 0.18 mm a product containing a dry matter of 94.5 wt %was obtained.

In table 15 the viscosity of the product is shown together with theviscosity of the corresponding non-extruded product.

Example 20

Dried seaweed of the species Iridaea ciliata was treated essentially asdescribed in example 18, the only difference being that the reactiontime was 1.5 hours and that the last (the 4th) washing step wasaccomplished with an aqueous solution of isopropanol (20 wt %)containing potassium chloride (5 wt %).

Table 14 shows the composition of the reaction mixture during the heattreatment.

A semi-dried product with a dry matter content of 49.1 wt % wasobtained. For purposes of comparison a smaller part of this product wasdried to a dry matter content of 94.0 wt % and ground to a particle sizeof less than 0.180 mm.

The semi-dried product was fed to the same extruder as used in example18 and processed under the following conditions:

    ______________________________________                                        Temperature of extruder:                                                      ______________________________________                                        Near the feed inlet:     80-85° C.                                     Central zone:            120-121° C.                                   Near the discharge end:  127-128° C.                                   Internal pressure near the discharge end:                                                              13-14 bar                                            Number of revolutions:   39 rpm                                               Torque:                  6-7 Nm                                               Back force:              0.4-0.5 kN                                           ______________________________________                                    

After drying the extruded product followed by grinding to a particlesize less than 0.18 mm a product was obtained containing a dry matter of95.2 wt %.

In table 15 the viscosity of the product is shown together with theviscosity of the corresponding non-extruded product.

                  TABLE 14                                                        ______________________________________                                        The composition of the reaction mixture                                       during the heat treatment                                                                Example 18  Example 19                                                                              Example 20                                   ______________________________________                                        Seaweed dry matter                                                            kg         12.95       13.08     15.60                                        wt %       16.0        16.0      18.8                                         Anhydrous KOH                                                                 kg         3.59        3.59      3.59                                         wt %       4.44        4.39      4.33                                         Anhydrous NaOH                                                                kg                     0.50                                                   wt %                   0.61                                                   Isopropanol                                                                   kg         12.0        12.0      12.0                                         wt %       14.9        14.7      14.5                                         Water                                                                         kg         52.26       52.63     51.61                                        wt %       64.68       64.30     62.30                                        Reaction mixture,                                                                        80.8        81.8      82.8                                         total weight, kg                                                              ______________________________________                                    

                  TABLE 15                                                        ______________________________________                                        Viscosity (expressed in cP) of the products obtained                          in examples 18-20 measured in demineralized water at                          75° C. and 30 rpm                                                                  Example 18  Example 19                                                                              Example 20                                  ______________________________________                                        Non-extruded product                                                                      24.8        66.0      141.0                                       Extruded product                                                                          18.6        68.4      150.0                                       ______________________________________                                    

Example 21

Dried seaweed material of the species Iridaea ciliata and Gigartinaskottsbergii, respectively, having a dry matter content of about 80 wt %was pre-treated by washing with an aqueous solution containing potassiumchloride (10 wt %).

The wet pre-washed seaweed was cut into pieces and treated in ahomogeneous alkaline solvent mixture comprising water, isopropanol andpotassium hydroxide at a temperature of 90° C. for 3 hours.

After completion of the heat treatment the solution was drained off andthe treated seaweed material was washed three times using 30%, 30% and35% by weight, respectively, of isopropanol/water mixtures. The treatedseaweed material of the species Gigartina skottsbergii was in additionto this washed with an aqueous solution of isopropanol (10 wt %)containing potassium chloride (5 wt %).

The washed seaweed material was partly dried to remove the organicsolvent giving a product (G. skottsbergii) with a dry matter content of40.0 wt % and a product (I. ciliata) with a dry matter content of 32.8wt %. For purposes of comparison a smaller part of the products weredried to a dry matter content of about 90 wt % (see table 17) and groundto a particle size of less than 0.180 mm.

The semi-dried products were fed to the same extruder as used in example18 and processed under conditions which are shown in table 16.

After extrusion the products were dried and ground to a powder with aparticle size of less than 0.180 mm.

The extruded and the non-extruded products were analyzed for starch andglucose. The results are shown in table 17.

                  TABLE 16                                                        ______________________________________                                        Operating conditions for shear stress and extrusion                           treatment in example 21                                                                      Iridaea   Gigartina                                                           ciliata   skottsbergii                                         ______________________________________                                        Temperature of extruder:                                                      Near the feed inlet:                                                                           88-90° C.                                                                          74-76° C.                                 Central zone:    123-124° C.                                                                        120-123° C.                               Near the discharge end:                                                                        133-135° C.                                                                        141-142° C.                               Internal pressure near the                                                                     10-11 bar   20-21 bar                                        discharge end:                                                                Number of revolutions:                                                                         39 rpm      96 rpm                                           Torque:          4-5 Nm      6-7 Nm                                           Back force:      0.3-0.4 kN  0.5-0.6 kN                                       ______________________________________                                    

                  TABLE 17                                                        ______________________________________                                        Content of starch and glucose in the                                          products of example 21                                                                      Dry matter Starch, Glucose,                                                   wt %       wt %    wt %                                         ______________________________________                                        Iridaea ciliata                                                               Extruded product                                                                            93.1       2.5     <0.3                                         Non-extruded product                                                                        93.0       2.5     <0.3                                         Gigartina skottsbergii                                                        Extruded product                                                                            93.8       4.3     <0.3                                         Non-extruded product                                                                        93.7       4.5     <0.3                                         ______________________________________                                    

As seen from table 17 the content of starch and glucose is unaffected bythe shear stress and extrusion treatment.

As seen from table 15 the ability of carrageenan to impart viscosity toaqueous solutions is preserved in the extruded products indicating thatthis treatment does not result in any essential degradation of thebiopolymer chain.

However, compared to base treated seaweed which has not been subjectedto shear stress, the products according to the invention are moreswellable and soluble in water. This is discovered when a suspension ofthe products in water is heated. Using a Brabender Visko-Amylograph theviscosity as a function of time and temperature is recorded. Theincrease of viscosity at first and later on a decrease in viscosity canbe directly correlated to hydration/swelling and dissolution of thecarrageenan particles.

As seen from table 18 the extruded products start swelling and come tomaximum swelling in a shorter time and at lower temperatures than do thenon-extruded products. Further, the degree of swelling is much higher.

                  TABLE 18                                                        ______________________________________                                        Temperature of hydration/swelling in water of the                             products obtained in example 18 and 19                                                          Temperature (°C.) of swelling                                          onset   maximum                                             ______________________________________                                        Ex. 18:  Non-extruded product                                                                         56        68                                                   Extruded product                                                                             54        60                                          Ex. 19:  Non-extruded product                                                                         52        70                                                   Extruded product                                                                             46        58                                          ______________________________________                                    

Apparatus: Brander Viskograph (type 801200); 60 rpm. Temperatureprogram: Heating 1.5° C./min, start 35° C., stop 95° C.

System: 3 wt % of product (example 18) or 2 wt % of product (example 19)suspended in 0.7 wt % aqueous potassium chloride. Total amount: 450 g.

Dispersed in water and stained with iodine, the powdered products withparticle size <0.180 mm showed distinct difference when viewed under alight microscope. In the base treated seaweed material which had notbeen extruded intact cell structures were clearly observed whereasextruded products only showed cell fragments embedded in particles ofrehydrated carrageenan gel (FIGS. 1-4).

I claim:
 1. A method of producing a semi-refined carrageenan comprisingthe steps of:(1) reacting a seaweed starting material containingcarrageenan, in a substantially homogeneous alkaline mixture of asolvent in which carrageenan is substantially insoluble, and an aqueousphase comprising an alkaline substance, to obtain at least partialformation in the carrageenan of 3,6-anhydro units, (2) separating theseaweed material from the reaction mixture of step (1) and subjectingthe seaweed material to at least one washing step with a solvent/watermixture, and (3) subjecting the seaweed material resulting from step (2)to shear stress.
 2. A method according to claim 1 wherein the seaweedstarting material is selected from the family Solieriaceae.
 3. A methodaccording to claim 2 wherein the seaweed material is selected from anEucheuma spp.
 4. A method according to claim 1 wherein the seaweedstarting material is selected from the family Gigartinaceae.
 5. A methodaccording to claim 4 wherein the seaweed material is selected from aGigartina spp.
 6. A method according to claim 4 wherein the seaweedmaterial is selected from an Iridaea spp.
 7. A method according to claim1 wherein the seaweed starting material is a mixture of materialselected from the family Solieriaceae and the family Gigartinaceae.
 8. Amethod according to claim 1 wherein the seaweed starting material is inthe form of pieces of at the most 5 cm in length.
 9. A method accordingto claim 1 wherein the reaction mixture of step (1) has a content ofseaweed dry matter which is in the range of 5 to 20 wt %.
 10. A methodaccording to claim 1 wherein step (1) is carried out at a temperature inthe range of 50° to 150° C.
 11. A method according to claim 1 whereinthe alkaline substance is selected from the group consisting ofhydroxides and carbonates of alkali metals, alkaline earth metals andammonium; alkali metal alcoholates; basic inorganic phosphates; andquaternary ammonium hydroxides.
 12. A method according to claim 1wherein the solvent is selected from the group consisting of monohydricalcohols, dihydric alcohols, trihydric alcohols, ketones and glycolethers.
 13. A method according to claim 1 wherein the substantiallyhomogeneous mixture further contains an added neutral salt selected fromthe group consisting of neutral salts of K, Na, Ca, Mg and Ba.
 14. Amethod according to claim 1 wherein the washing step is at a temperaturein the range of 20° C. to 100° C.
 15. A method according to claim 1wherein the solvent in the solvent/water mixture is selected from thegroups consisting of monohydric alcohols, dihydric alcohols, trihydricalcohols, ketones and glycol ethers.
 16. A method according to claim 1wherein the solvent/water mixture further contains an added neutral saltselected from the group consisting of salts of K, Na, Ca, Mg and Ba. 17.A method according to claim 1 wherein the weight ratio between solventand water in a first washing step is from 15:85 to 60:40.
 18. A methodaccording to claim 1 wherein the weight ratio between solvent and waterin a further washing step is from 25:75 to 99:1.
 19. A method accordingto claim 1 wherein the concentration of alkaline substance in thereaction mixture of step (1) is in the range of 0.25M to 3.0M/kg liquidphase.
 20. A method according to claim 1 wherein the weight ratiobetween solvent and water in the reaction mixture of step (1) is from5:95 to 50:50.
 21. A method according to claim 1 wherein the seaweedmaterial resulting from step (2) is dried to a dry matter content of atleast 30 wt %.
 22. A method according to claim 1 wherein the shearstress is provided by means of an extruder.
 23. A method according toclaim 1 wherein the seaweed material resulting from step (2) issubjected to shear stress at a temperature in the range of 40° to 175°C.
 24. A method according to claim 1 wherein the seaweed material issubjected to shear stress for a period of time being in the range of 10to 200 seconds.
 25. A method according to claim 1 wherein the seaweedmaterial subjected to shear stress comprises at least one further addedsubstance selected from the group consisting of inorganic acids, bases,salts, flavoring agents, coloring agents, emulsifiers, non-carrageenanhydrocolloids, anti-microbial agents and mixtures thereof.
 26. A methodaccording to claim 1 wherein the seaweed material resulting from step(3) is subjected to a further process step selected from comminution anddrying to a dry matter content of at least 85 wt %.
 27. Acarrageenan-containing product obtainable by a method as defined inclaim 1 which,(i) when measuring a 2-3 wt % suspension of the producthaving a dry matter content of at least 90 wt % and an average particlesize of less than 0.18 mm, in a 0.7 wt % aqueous solution of KCl bymeans of a Brander Viscograph operated at 60 rpm and at a heating rateof 1.5° C./min from an initial temperature of 35° C., shows a maximumswelling at a temperature which is at the most 65° C. and which, (ii)when measured in the form of a water gel containing 0.126% dry matter ofthe product by means of a spectrophotometer at a wavelength of 420 nm ina cuvette with a light path of 1 cm exhibits a light transmission of atleast 5%.
 28. A product according to claim 27 which is produced from aseaweed species of the family Gigartinaceae, having a content of drymatter of at least 85 wt % and showing at least one of the followingcharacteristics:a) a content of acid insoluble matter of at the most 2%by weight; b) a nitrogen content of at the most 0.25% by weight; c) acellulose content of at the most 2.0% by weight; and d) a starch contentof at the most 10% by weight.
 29. A product according to claim 28showing at least two of the characteristics a through d.
 30. A productaccording to claim 28 which is a cream-colored powder.
 31. A productaccording to claim 28 which has no off-flavor.
 32. A product accordingto claim 27 which is produced from seaweed of the family Solieriaceae,having a content of dry matter of at least 85 wt % and showing at leastone of the following characteristics:a) an acid insoluble matter contentof at the most 13.0% by weight; b) a nitrogen content of at the most0.25% by weight; c) a content of cellulose of at the most 9.0% byweight; d) a starch content of at the most 4.5% by weight.
 33. A productaccording to claim 32 showing at least two of the characteristics athrough d.
 34. A product according to claim 32 which is a cream-coloredpowder.
 35. A product according to claim 32 which has no off-flavor.